The invention relates to a composite panel that is difficult to combust, produces little smoke and can be shaped at room temperature by non-chip-forming methods, said panel comprising a core layer of thermoplastic plastic between metal outer sheets bonded to the same by adhesive layers, and relates also to a process for manufacturing the said composite panel.
Known composite panels that can be shaped at room temperature using non-chip-forming methods i.e. by bending, stretch drawing and/or stretch deep-drawing, have plastic cores of polyolefins or polyvinylchloride. A composite havinq a polyolefin core is classified according to the known specifications e.g. DIN 4102 as having "normal combustibility", which can result in limitations in its application.
A composite having a core of polyvinylchloride, in particular hard polyvinylchloride is classified according to DIN 4102 as being "difficult to combust" which permits a wider range of application.
A disadvantage of the hard polyvinylchloride core is however the amount of smoke it produces in a fire. Such core layers in the form of compact, hard polyvinylchloride exhibit smoke index values, measured according to ASTM E-84, of 900-1400 and in the form of foamed hard polyvinylchloride containing flame retardant, values of 500-1400. Such composite panels, containing a core having a smoke index value of more than 450, are not classified as materials of combustibility class 1 or class A of the US Building Model Codes; this standard is usually taken for reference purposes where national standards of that kind are lacking.